This invention relates to a novel process for coating of vulcanized saturated or unsaturated polyolefin rubber articles with an isocyanate-curing varnish.
It is not customary to varnish vulcanized rubber articles, since they are utilized predominantly for their functional characteristics rather than their appearance. However, exceptions are known in the case of certain rubber materials employed in connection with articles substantially affected by the design of the article, e.g., coated vulcanized articles of saturated or unsaturated polyolefin rubbers employed in the automobile industry.
"Rubber World," February 1972, pp. 31 et seq., discloses a process for varnishing vulcanized unsaturated ethylenepropylene rubber articles with isocyanate-curing varnishes. In this process, the surface of the article to be varnished is pretreated in a multistage process involving cleaning, sensitizing and UV radiation. Following this pre-treatment, the actual varnishing is carried out in a two-stage process in which a primer is first applied over which, after curing, is applied a top coat of varnish.
This state-of-the-art process is complicated, due to its many process steps, and thus is uneconomical.
Therefore, it is an object of this invention to develop a coating process in which a coating is applied to vulcanized saturated or unsaturated polyolefin rubber articles in a simpler manner, using isocyanate-curing varnishes to provide a coating which has good adhesion, high elasticity, a scratch-proof surface and optionally, high gloss. Other objects will be apparent to those skilled in the art to which this invention pertains.